The $600-million collapse of Allied Deals Inc. has proved to be the final straw for many lenders to the metals industry in the United States--banks that are now shutting down, scaling back or renegotiating with customers they once courted as attractive business prospects.

The IOUs that Kaiser Aluminum Corp. accumulated right up to its Chapter 11 bankruptcy protection filing were formidable, but some scrap suppliers and others were given a heads-up and got paid before debts were frozen.